Sanitary filtration plant with helical filter elements

ABSTRACT

A sanitary filtration plant including an oblong, tubular pressure vessel having one or more helical filter elements. Each helical filter element has a spiral-wound filter member and a central tube and, at an outlet end, a supporting structure formed as a wheel with a hub, spokes and a rim. The plane side of the downstream face of each supporting structure is provided with a plurality of recesses that are positioned between an opening between the spokes and the external periphery of the rim and extend circumferentially so as to be substantially concentric with said rim.

This is a nationalization of PCT/DK01/00837 filed Dec. 19, 2001 andpublished in English.

TECHNICAL FIELD

The invention relates to a sanitary filtration plant comprising anoblong, tubular pressure vessel, which includes one or more helicalfilter elements, each helical filter element comprising a spiral-woundfilter member and a central tube as well as a supporting means at oneend which represents the outlet end while the plant is operating, saidsupporting means being in form of a wheel with a hub, spokes and rim andcentrally being provided with a transition member which is adapted toensure a sealing flow connection between adjacent ends of adjacentcentral tubes, and where each supporting means comprises plane sides forabutment against the ends of the filter members of the adjacentrespective helical filter element(s) and along the external periphery isprovided with a sealing means for a sealing abutment against the innerside of the pressure vessel. The invention relates furthermore to asupporting means to be used in such a sanitary filtration plant.

BACKGROUND ART

Sanitary filtration plants of the above type are known which comprisejoined helical filter elements connected in series and mounted inside apressure pipe, and where the product in question passes through thefilter member while subjected to a suitable pressure difference. Fromthe filter member, the permeate flows into the connected central tubesand leaves said tubes while separated from the concentrate. Theconcentrate passes through the filter member and leaves the pressurepipe while separated from the permeate. The helical filter elements canbe of a length of approximately 0.5 to 1.0 m and have a tendency to besubjected to an axial displacement of the filter member relative to thecentral tube, viz. a so-called telescoping. Therefore, supporting meansare arranged between the helical filter elements in order to counteractsaid displacement, said supporting means being so-calledanti-telescoping devices, viz. ATD's. These supporting means also serveto ensure that the product to be filtered does not pass the filterelements freely between the external periphery thereof and the innerside of the tubular pressure vessel as a slit is provided at thislocation. This slit originates from an overdimensioning of the pressurevessel and allows an easy mounting and replacement of the filterelements. The latter prevention of the free flow through this slit isenhanced by the supporting means comprising a sealing means along theexternal periphery.

A filtration device with supporting means of a similar type is knownfrom U.S. Pat. No. 4,517,085. However, this helical filtration device isnot suited for use as a sanitary filtration plant.

A sanitary filtration plant used inter alia within the dairy, themedicine and the food-stuff industry presents very high requirements tothe hygiene. A continuous use of a sanitary filtration plant oftennecessitates a cleaning, such as once or twice a day, whereby a cleaningfluid passes through the plant. It is important in connection with sucha cleaning process that residues of the product in question are removed.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to provide a sanitary filtration plantwhich ensures such an efficient cleaning.

This object is according to the invention obtained by the filtrationplant described in the introduction being characterised in that aplurality of recesses extending between an opening between spokes andthe external periphery of the rim is provided in the plane side of thesupporting means being the downstream face while the plant is operating.

As a result, a controlled flow is ensured of both the product to besubjected to a filtration and the cleaning fluid on the downstream faceof the supporting means in such a manner that a flow of the fluid inquestion is carried directly into the area behind the sealing means ofthe supporting means, whereby this area behind the sealing means iswashed with the result that a replacement of both the product to besubjected to a filtration and the cleaning fluid is ensured. Inaddition, the pressure prevailing inside the slit on the outer side ofeach helical filter element is equalized along the entire length of saidhelical filter element with the result that the efficiency of the plantis increased and the above telescoping is minimized.

According to the invention it is particularly advantageous when a recessextends from each opening between the spokes of the supporting means.

The invention relates also to a supporting means to be used in asanitary filtration plant of the above type. This supporting means isaccording to the invention characterised in that it is provided with aplurality of recesses in the plane side being the downstream face whilethe plant is operating, said recesses extending between an openingbetween the spokes and the external periphery of the rim.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below with reference to theaccompanying drawings, in which

FIG. 1 is a cross-sectional view through a portion of a filtration plantaccording to the invention, whereby parts have been omitted for the sakeof clarity, and is a sectional view taken along the central line and inform of solid lines below said central line through the supporting meansprovided between the helical filter elements,

FIG. 2 illustrates on a larger scale the supporting means, seen from thedownstream face thereof, and

FIG. 3 is a sectional view taken along the line A—A of FIG. 2 of thesupporting means shown in FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

The filtration plant shown in FIG. 1 comprises a pressure pipe 1, inwhich three helical filter elements 2, 3 and 4 are mounted. Each helicalfilter element 2, 3 and 4 comprises a spiral-wound filter member 5, 6and 7, respectively, arranged about a central tube 8, 9 and 10,respectively. These helical filter elements 2 to 4 are of aconventionally known type.

A plug means 11 is provided at the right end of the row of helicalfilter elements 2 to 4 shown in the drawing, said plug means 11comprising a centrally projecting projection 12 with an external seal 13for sealingly engaging and closing the central tube 10. This plug meansis of a conventionally known type with radially projecting wings 14, 15,16, 17 and 18 for a supporting abutment against the adjacent end of thefilter member 7.

A supporting means 19, 20 and 21 is arranged between the helical filterelements 2 to 4 and at the left end of the row of said filter elements 2to 4 in the drawing. As shown in FIGS. 2 and 3, each supporting meanscomprises a hub 22, radial spokes 23 to 30 as well as a rim 31 with theresult that these supporting means are of a wheel-like shape. Aprojecting projection 32, 33 is centrally arranged on each side of thesupporting means, said projections 32, 33 defining a through bore 34centrally arranged in the hub. These projections serve to form atransition means 35 between abutting ends of the central tube of therespective helical filter elements 2 to 4, said projecting projections32 and 33 sealingly engaging said central tubes 8 to 10 by means of acircumferential sealing means 36, 37, respectively.

The transition means at the left end of the row of filter elements 2 to4 shown in FIG. 1 co-operates with a centrally arranged tube 38 servingto carry the permeate away from the filtration plant.

FIG. 3 illustrates particularly clearly that the supporting means 19, 20and 21 externally comprise a circumferential lip seal 39 which isreceived and vulcanized in a circumferential groove 40.

As particularly clearly shown in FIGS. 2 and 3, but also in FIG. 1,radial recesses 41 to 48 are provided on one side of each supportingmeans 19 to 21, and in greater detail on the side of the supportingmeans forming the downstream face of said supporting means while thefiltration plant is operating. These recesses 41 to 48 extend betweentheir respective openings between the spokes 23 to 30 and the outer sideof the rim 31.

A product to be filtered by means of the filtration plant is carriedthrough the row of filter elements 2, 3 and 4, cf. the arrows at theright end of FIG. 1. The permeate or the filtrate leaves the filtermembers 5 to 7 in a conventionally known manner and flows into thecentral tubes 8, 9 and 10 and then out of said tubes through the tube 38to the left of FIG. 1. The remaining portion of the product to befiltered, viz. the concentrate, leaves also to the left so as to bedrained off in a conventionally known manner.

As illustrated in FIG. 1, a circumferential slit 49, 50 and 51 isprovided between the individual filter elements 2 to 4 and thesurrounding pressure pipe 1. These slits are present in order tofacilitate the mounting and the replacement of the filter elements 2 to4. A portion of the product to be filtered does, of course, pass roundthe first filter element 4, but is prevented from flowing directly fromthe surrounding slit 51 and further to the succeeding slit 50 by meansof the lip seal 39 on the supporting means 21 arranged therebetween. Thepresence of the lip seal 39 forces the product through the filter member7 of the helical filter element 4, and the concentrated portion thereofleaves the filter member 7 and flows between the spokes of thesupporting means 21 and into the filter member 6 of the succeedingfilter element 3. However, a portion of the concentrate flows directlythrough the recesses 41 to 48 and directly into the surrounding slit 50.The same procedure takes place at the next supporting means 20. At thelast supporting means 19, the concentrate is also forced into the filtermember 5 of the filter element, where the portion not filtered off flowson in form of a concentrate.

Thus the recesses 41 to 48 on the rear side of the supporting means 19to 21 ensure that fresh fluid is continuously fed to the area behind therespective lip seals 39 in such a manner that the fluid in said area iscontinuously replaced. The latter procedure is also carried out duringthe periodic cleaning processes, whereby a cleaning fluid is fed throughthe filtration plant.

The direct flow of fluid out through the recesses 41 to 48 impliesduring the operation of the filtration plant that a constant and uniformpressure is maintained in the slits 49 to 51 between the helical filterelements 2 to 4 and the pressure pipe 1, and consequently the load onthe helical filter elements 2 to 4 is equalized along the entire lengththereof. The direct filling of the slits through the recesses impliesfurthermore that these slits are not to be filled with fluid which firstmust pass through portions of each helical filter element 2 to 4. Thusthe presence of the recesses results in an optimized effect of thehelical filter elements and consequently in a prolonged life of saidhelical filter elements.

The invention has been described with reference to a preferredembodiment. Many modifications can be carried out without therebydeviating from the scope of the invention. The plant can for instancecomprise only one helical filter elements or more helical filterelements arranged in parallel.

The recesses 41 to 48 can for instance be of a varying shape and lengthin the circumferential direction. Outside the recesses 41 to 48, the rim31 and the spoke 23 to 30 are substantially plane both on the front sideand on the rear side of the supporting means 19 to 21 with the resultthat they directly abut the ends of the adjacent helical filterelements.

The invention being thus described, it will be apparent that the samemay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be recognized by one skilled in the art areintended to be included within the scope of the following claims.

1. A sanitary filtration plant comprising: an oblong, tubular pressurevessel defining a pressure pipe and including at least one helicalfilter element having a spiral-wound filter member, at least one slitbetween a respective filter element and the pipe and a central tube; asupporting structure at an outlet end of said helical filter elementwith respect to plant operation, said supporting structure being in formof a wheel with a hub, spokes and a rim and having plane sides forabutment against the outlet end of the filter member, said supportingstructure further being provided along an external periphery thereofwith a sealing element for sealing abutment against an inner side of thepressure vessel and a plurality of recesses positioned between at leastone opening between the spokes and an external periphery of said rim andfluidly communicating with the respective slit, said recesses beingprovided in the plane side of the supporting structure on a downstreamface thereof while the plant is operating.
 2. The sanitary filtrationplant according to claim 1, wherein a recess extends circumferentiallyadjacent each opening between the spokes of the supporting structure. 3.The supporting structure according to claim 1, wherein said supportingstructure further includes a transition element adjacent said hub whichis adapted to ensure a sealing flow connection between adjacent ends ofadditional central tubes.
 4. The supporting structure according to claim1, wherein said supporting structure further includes a sealing elementalong an external periphery of said rim.
 5. The supporting structureaccording to claim 1, wherein a plurality of said supporting structuresare used in a sanitary filtration plant having a plurality of helicalfilter elements arranged in series, each of said supporting structuresbeing in abutment with a downstream face of a respective helical filterelement.
 6. The supporting structure according to claim 5, furthercomprising a transition element adjacent each hub of said plurality ofsupporting structure, said transition element being adapted to ensure asealing flow connection between adjacent ends of central tubes of saidplurality of helical filter elements.
 7. A sanitary filtration plantcomprising: an oblong, tubular pressure vessel defining a pressure pipeand having a plurality of helical filter elements arranged adjacent oneanother, each helical filter element including a spiral-wound filtermember, a plurality of slits between respective filter elements and thepipe, and a central tube; a plurality of supporting structures at outletends said helical filter elements with respect to plant operation,respectively, each of said supporting structures being in the form of awheel with a hub, spokes and a rim, said supporting structures havingplane sides for abutment against said outlet ends of the filter membersof the respective adjacent helical filter elements, each of saidsupporting structures having a plurality of recesses positioned betweenat least one opening between the spokes and the external periphery ofthe rim and fluidly communicating with the respective slits, saidrecesses being provided the plane side of each supporting structure on adownstream face thereof while the plant is operating.
 8. The sanitaryfiltration plant according to claim 7, wherein a recess extendscircumferentially adjacent each opening between the spokes of each ofsaid supporting structures.
 9. The sanitary filtration plant accordingto claim 7, wherein said supporting structure is provided with atransition member adjacent said hub which is adapted to ensure a sealingflow connection between adjacent ends of adjacent central tubes ofadjacent filter elements.
 10. The sanitary filtration plant according toclaim 7, further comprising a sealing element along an externalperiphery of said rim for sealing abutment against an inner side of thepressure vessel.